Electronic devices typically make use of both analog and digital signals. An analog signal is a continuous signal which may assume any value. A digital signal is one which may assume one of a discrete set of values. A signal may be in the form of an electrical current or a voltage. Electrical current is the measurement of the flow of electrons. Voltage may be defined as the difference between electric potential at two given points.
Electronic circuitry often includes devices for transferring analog signals into digital signals and vice versa. For example, a Digital-to-Analog Converter (DAC) is used to transfer digital signals into analog signals. Some DACs are configured to output a differential signal. A differential signal is output on a positive terminal and a negative terminal. The value of the signal may be taken as the value of the signal on the positive terminal subtracted by the value of the signal on the negative terminal. Similarly, some DACs may be configured to accept complimentary digital signals at their input. Two digital signals are complimentary when the signals are logical compliments of each other. The output of a DAC is often connected to other circuit devices. The performance of such circuit devices is affected by the output capacitance of the DAC.
The output capacitance of the positive and negative terminals of a DAC generally depends on the code used by the DAC as well as the digital input received by the DAC. Thus during normal operation, the output capacitance of the DAC may vary according to the input signal.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.